Fix: Correct typings for List and Dict

In python 3.8 the typings list[...] and dict[...] raise the error TypeError: 'type' object is not subscriptable. This merge request makes use of the "proper" typings for dict and list. In 3.9+ this is not an issue, but the new typings remain the proper way to do things as far as I know.

Generator was also updated to come from typings instead of collections.abc